# std::chrono::operator+, std::chrono::operator- (std::chrono::year_month_weekday_last)

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< cpp‎ | chrono‎ | year month weekday last

constexpr std::chrono::year_month_weekday_last operator+( const std::chrono::year_month_weekday_last& ymwdl, const std::chrono::months& dm ) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_weekday_last operator+( const std::chrono::months& dm, const std::chrono::year_month_weekday_last& ymwdl ) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_weekday_last operator+( const std::chrono::year_month_weekday_last& ymwdl, const std::chrono::years& dy ) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_weekday_last operator+( const std::chrono::years& dy, const std::chrono::year_month_weekday_last& ymwdl ) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_weekday_last operator-( const std::chrono::year_month_weekday_last& ymwdl, const std::chrono::months& dm ) noexcept; |  | (since C++20)
constexpr std::chrono::year_month_weekday_last operator-( const std::chrono::year_month_weekday_last& ymwdl, const std::chrono::years& dy ) noexcept; |  | (since C++20)

1,2) Adds dm.count() months to the date represented by ymwdl. The result has the same `year()` and `month()` as std::chrono::year_month(ymwdl.year(), ymwdl.month()) + dm and the same `weekday()` as ymwdl.
3,4) Adds dy.count() years to the date represented by ymwdl. The result is equivalent to std::chrono::year_month_weekday_last(ymwdl.year() + dy, ymwdl.month(), ymwd.weekday_last()).
5) Subtracts dm.count() months from the date represented by ymwdl. Equivalent to ymwdl + -dm.
6) Subtracts dy.count() years from the date represented by ymwdl. Equivalent to ymwdl + -dy.

For durations that are convertible to both std::chrono::years and std::chrono::months, the `years` overloads (3,4,6) are preferred if the call would otherwise be ambiguous.

### Example

Run this code

    #include <cassert>
    #include <chrono>
    using namespace std::chrono;

    int main()
    {
        constexpr auto ymwdl1{Tuesday[last]/11/2021};
        auto ymwdl2 = ymwdl1;
        ymwdl2 = std::chrono::months(12) + ymwdl2;
        ymwdl2 = ymwdl2 - std::chrono::years(1);
        assert(ymwdl1 == ymwdl2);
    }

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